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92landyacht 07-09-2014 03:54 PM

Arghh!! Generator shutting off
 
Just got back from a 4th of July trip and everything went well except for the generator. Some times it runs for a couple hours and sometimes it will only run for 10 minutes. Every time it sputters and quits. Checked the oil level and that's OK. Sounds like it's running out of fuel. The Genset is a Onan NHM Marquis 7KW unit. Guess I've got some troubleshooting to do.:bb:

AdamB 07-09-2014 10:55 PM

Fuel filter or low fuel level? Mine is surely different (Powertech/Kubota 7000W diesel running off the 90 gal main fuel tank), but it won't work without at least 1/4 tank of fuel in the tank. I also went through about 4 fuel filters when I got my motorhome 3 years ago to clear all the junk out of the lines. It kept stalling on our first trip until I went through at least 3 fuel filters. I also changed the air filter, oil & oil filter later. It runs great now and we do a lot of camping in county, state & national parks w/o hookups and we rely on our genset a lot.


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J. Morgan 07-10-2014 12:48 AM

Maybe getting hot and/or vapor lock?

Gas ain't what it was, with fuel injection becoming the rule, gasoline boiling temperature has dropped, so I have read anyway.

(Since gas constantly recirculates with fuel injection, it is not sitting in one place to get hot so the boiling point is not as critical as it used to be)


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92landyacht 07-10-2014 07:32 AM

Quote:

Originally Posted by AdamB (Post 1480518)
Fuel filter or low fuel level? Mine is surely different (Powertech/Kubota 7000W diesel running off the 90 gal main fuel tank), but it won't work without at least 1/4 tank of fuel in the tank. I also went through about 4 fuel filters when I got my motorhome 3 years ago to clear all the junk out of the lines. It kept stalling on our first trip until I went through at least 3 fuel filters. I also changed the air filter, oil & oil filter later. It runs great now and we do a lot of camping in county, state & national parks w/o hookups and we rely on our genset a lot.


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Tank is over 3/4 full so I don't think that it's the problem. I was able to pump a quart of fuel out into a clear container and found no debris in the fuel. Fuel filter is not obstructed.

Today I added a fuel gauge after the fuel filter. I ran it until it quit (about 1.5 hours). I tried to restart it but it would not build any fuel pressure. I disconnected the fuel line and could see only a dribble of fuel when cranking. I sucked on the fuel line while cranking and found no obstruction to fuel flow. Conclusion at this point is that the fuel pump is going out. I ordered a Carter P4070 fuel pump. The OEM pump sells for over $230 and is made by Carter. Same shape and the same output pressure (4-6psi). I'll update once the pump arrives. Not looking forward to installing it though.:unhappy:

bkahler 07-10-2014 09:15 AM

Another possibility is the suction line (from fuel pump to tank) has cracks in it. Your Land Yacht will cause all sorts of running and starting problems for the generator.

Worth checking into.

Brad

92landyacht 07-11-2014 02:35 PM

Quote:

Originally Posted by bkahler (Post 1480619)
Another possibility is the suction line (from fuel pump to tank) has cracks in it. Your Land Yacht will cause all sorts of running and starting problems for the generator.

Worth checking into.

Brad

Good point Brad. I'm actually hoping that it's the pump since tracking down a leak in the fuel line could become even more problematic.

I'm thinking the fuel pump will do it since the pump couldn't pull any fuel but I was easily able to pull fuel by simply sucking on the fuel line. It seemed like the pump had no prime capability. The fuel was clearly right there at the pump, since it took nothing to get fuel to flow with a light vacuum on the line, but the pump still couldn't push any volume or build pressure. Almost like the pump was stalled. I'll let you know since I just got notice that the pump arrived at the house.

Probably going to bypass the current pump and let the new pump pull fuel from the original line to test it. That will tell me if the original pump is bad before I go ahead and attempt to yank the old one out.

bel73 07-11-2014 04:35 PM

Also check the vent in the cap. If it is clogged up it will cause a vacuum in the tank and not let the fuel flow. This happened to me once on my riding mower. After I changed the filter, plug and cleaned the carb twice I finally figured it out.

Try running it with the cap loose to see if it still dies.

92landyacht 07-11-2014 07:17 PM

I would think that the engine would have issues then as well. The 454 engine has no issues with running down the road for hours. It draws from the same tank as the genset and pull a ton more fuel/hour.

Replacement fuel pump arrived today. Carter P4070. Looks identical to the OEM Onan pump and has the same pressure rating at 4-6psi. Once I remove the original pump I'll be able to compare item to item. Price difference alone is worth the experimentation. $230 v/s $64 delivered.

Farmer Dan 07-11-2014 09:05 PM

This is a simple suggestion that may or may not work. Get some Sea Foam gas treatment and put in the gas tank. You may have a jet or small passage that is partially gummed up on the genny carb. This additive works for us on small engines on the farm whether its seed tenders, lawn mowers or ATVs with Honda power, Briggs & Stratton or Yamaha power. I usually end up with it mixed stronger than recommended, but have no problems. I think its a petroleum product anyhow. It'd be an easy try.
Dan

hissilver 07-11-2014 09:07 PM

One other source for your problem may be a fleck of carbon has attached itself to the spark plug and is not allowing the spark to fire and ignite the pressurized fuel...just a thought

92landyacht 07-12-2014 06:36 AM

Guys, thanks for the input. I've confirmed that, when the problem is occurring, no gas comes out the fuel line when the gen is cranking. After sitting for a while it will pump gas but not for more then a couple hours. Sometimes for a little as 10 minutes. If I feed gas to the carb it starts and runs fine. I figure I'll be able to try to bypass the pump on Weds if weather permits. That will tell me if it's a pump or feed line issue. It's not a gummed up carb problem for sure. Whenever I put gas in the MH I add the appropriate amount of STA-BIL fuel stabilizer.

bkahler 07-12-2014 07:11 AM

2 Attachment(s)
Quote:

Originally Posted by 92landyacht (Post 1481264)
I would think that the engine would have issues then as well. The 454 engine has no issues with running down the road for hours. It draws from the same tank as the genset and pull a ton more fuel/hour.

One thing to keep in mind, the genset has a different tap into the fuel tank than the 454 engine tap. The genset tap doesn't stick down into the tank as far which means you can't inadvertently suck the tank dry while camping in the middle of nowhere :lol:

Quote:

Replacement fuel pump arrived today. Carter P4070. Looks identical to the OEM Onan pump and has the same pressure rating at 4-6psi. Once I remove the original pump I'll be able to compare item to item. Price difference alone is worth the experimentation. $230 v/s $64 delivered.
That's good to know. Where did you order the pump from?

I've attached a couple of pictures of how I did the suction line plumbing on the Kohler in the 310 I used to own.

Attachment 216189Attachment 216190

I bought two 1/4" plastic shutoff valves like those used on lawn mowers, etc and also a 1/4" plastic Tee. One shutoff valve goes in the suction line to the coach fuel tank. The other shutoff valve is on the other side of the Tee and I attached about a 5' or 6' long piece of hose to the other Tee that I use to stick into a gas can for testing purposes or if I just want to run the genset for a while without pulling fuel from the main tank.

You have to keep one of the valves closed all the time or the pump won't be able to generate any suction. This arrangement has come in handy several times when I had to troubleshoot problems with the starting/running of the Kohler genset.

Simple and cheap to do and it seemed like a worth while modification.

Brad

bkahler 07-12-2014 07:20 AM

Quote:

Originally Posted by 92landyacht (Post 1481385)
Whenever I put gas in the MH I add the appropriate amount of STA-BIL fuel stabilizer.

That's something I should be doing as well. Just need to remember to do it :)

92landyacht 07-12-2014 11:05 AM

Ya, I keep a quart of STA-BIL in one of the lower compartments near the fuel inlet. I figure about how much I'm going to need to fill or put in and dump one Oz per 5 gallons in before I fill. Haven't had a gas related problem for years. Even after sitting for months.


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